It has become increasingly common for beverages such as soft drinks to be sold in bottles made of plastic. Bottles made of the plastic polyethylene terephthalate (PET) have become especially popular with the soft-drink industry because of their transparency, light weight and low cost. Such bottles are available in a wide range of capacities, including 16 ounce, half-liter, one-liter, two-liter, three-liter and four-liter.
Two types of PET bottles are generally used by soft drink bottlers today: a base-cup type and a petaloid type. Both types of PET bottles are generally symmetric in shape, having a longitudinal symmetry axis.
Conventional PET bottles of the base-cup type have three parts: a vessel made of PET plastic for containing the beverage, a closure for sealing the vessel, and a base cup. The base portion of the PET vessel is generally hemispherical in shape and thus does not provide a surface on which the bottle can stand upright. The base cup is a separately formed piece which is adhesively bonded to the hemispherical base portion of the PET vessel and has a bottom which is shaped to permit the bottle to stand upright on a flat horizontal surface. An annular indentation is formed in the bottom of the base cup to provide a surface for bonding the base cup to the PET vessel.
Conventional PET bottles of the petaloid type have only two parts: a petaloid vessel made of PET plastic and a closure for sealing the vessel. Typically, the base portion of the PET petaloid vessel has six petaloid lobes projecting from it in a generally circular arrangement. Bottom surfaces of the lobes are generally substantially coplanar with respect to one another and permit the bottle to stand upright on a horizontal flat surface.
Although the walls of PET bottles are flexible, they are strong in tension and thus can contain the pressure of carbonated beverages safely. Moreover, conventional PET bottles of either the base-cup or the petaloid type can bear a surprisingly high compressive load when filed with carbonated beverage if the load is directed substantially along the longitudinal symmetry axis of the bottle. A single PET bottle filled with carbonated beverage can support the weight of many bottles of the same size filled with beverage if the bottle in question is standing upright and the weight of the other bottles is applied to the closure of the single bottle and is directed substantially vertically along the symmetry axis. However, if a compressive load is applied to a conventional PET bottle along a direction other than the symmetry axis of the bottle, the bottle tends to buckle and give way.
Cases of bottles of soft drinks are customarily stacked one on top of the other for warehousing and shipment. U.S. Pat. No. 4,344,530 of deLarosiere (the '530 patent) discloses a molded plastic case which may be loaded with PET bottles and stacked stably. The case has bottle pockets which are shaped to fit closely the bases of bottles inserted in the pockets and so to orient the bottles along the centerlines of the pockets. Thus, bottles seated in the pockets are oriented so that the weight of a stack of cases of bottles filled with beverage is properly transmitted along the longitudinal symmetry axes of the bottles. The '530 patent refers specifically only to PET bottles of the base-cup type, although teachings of the patent are applicable to PET bottles of the petaloid type as well. The specific cases exemplified in the '530 patent are only suitable for transporting PET bottles of the base-cup type.
A problem arises in attempting to design a case with bottle pockets shaped to orient the bases of PET bottles of both the base-cup type and the petaloid type. Conventional PET bottles of the petaloid type generally have a significantly smaller outside diameter than conventional PET bottles of the base-cup type with the same capacity. As a result, a bottle pocket with an inside diameter dimensioned to fit a PET bottle of the base-cup type sufficiently closely to orient the bottle stably ordinarily fits a PET bottle of the petaloid type so loosely as not to orient the bottle with sufficient stability to permit the case to be used for stacking in commercial bottling operations.
A molded plastic case marketed by Rehrig-Pacific Co., Inc. of Los Angeles, Calif. under the trade designation "PLBC 8-2L (QD)" (the Rehrig-Pacific case) has eight bottle pockets adapted to carry two-liter PET bottles of the base-cup type. An open network of ribs forms the floor of the bottle pockets in the case. The floor of each bottle pocket is essentially flat except for six studs which project outward from the floor into the bottle pocket. The six studs are spaced at intervals about a circle and are shaped to fit within the annular indentation in the base cup of a PET bottle of the base-cup type. The studs in the bottle pockets of the Rehrig-Pacific case are sufficiently short and the gaps between the studs are sufficiently wide that the studs can fit between the petaloid lobes of a conventional PET bottle of the petaloid type seated in a bottle pocket. When a conventional two-liter PET bottle of the petaloid type is seated in a bottle pocket of the Rehrig-Pacific case, the bottom surfaces of the petaloid lobes rest on the floor of the bottle pocket approximately between the studs. For certain conventional PET bottles of the petaloid type, the structure of the Rehrig-Pacific case generally provides insufficient stacking stability for use in a typical commercial bottling operation.
A commercial soft-drink bottling operation typically requires a "float" of tens of thousands of cases to warehouse PET bottles of soft drinks and to deliver the bottles to retail stores. A need exists for a reusable case which permits stable stacking of the cases of PET bottles of both the base-cup type and the petaloid type, so that a soft-drink bottler can switch from one type of PET bottle to the other as market conditions dictate without having to replace the float of cases used to warehouse and deliver the bottles.